The present invention relates to tufting machines, and more particularly, to a novel method and apparatus for inserting more tufts into a backing fabric to produce a novel fabric of very high pile density.
In the past it has been known to use an intermittent step-by step feeding mechanism for the feeding of the backing fabric longitudinally through a tufting machine. One such arrangement is shown in U.S. Pat. No. 2,411,267, but as in other such arrangements the fabric is fed each time the needle bar is raised. Thus, each needle makes one penetration in each lateral or transverse row.
It is also been known to initiate relative lateral movement between the backing fabric and the needles of the machine in order to relatively laterally displace longitudinal rows of stitching and thereby provide patterning effects. Examples of this method are disclosed in U.S. Pat. Nos. 2,411,267, 3,026,830 and 3,301,205. However, when using such relative lateral displacement with a continuous feeding or with the known intermittent step-by-step mechanisms, the gauge of the fabrics, i.e., the spacing between adjacent needle penetrations in each lateral or transverse row, is not different than the gauge or distance between adjacent needles. The density of the finished fabric is related to the gauge of the fabric and this in turn has been limited by the needle gauge.
Two approaches to increasing the density are disclosed in U.S. Sts. Pat. Nos. 3,577,943 and 3,596,617. In the former patent the spacing of the tufts are spaced less than the full needle gauge by shifting the needle plate while maintaining the loops on the loopers and while penetrating the needles into the backing fabric so as to restrain the lateral shifting of the backing fabric while the shifting mechanism continues to shift relative thereto. This machine, however, requires a critical timing of the needles, loopers and shifting mechanism. In the latter patent the needle can be shifted a distance less than its actual gauge by simultaneously shifting the other gauge parts, i.e., the looper and cutting knife, so that the gauge parts remain in registry during relative movement. However, construction of this mechanism was found to be extremely complex.
In all these known prior art attempts to increase the fabric density each needle effects a zig-zag penetration of the backing fabric and thus even though there is a gauge reduction of the finished fabric, the density is not as great as a machine incorporating a smaller needle gauge equal to the transverse spacing of the penetrations. However, it was the space limitations of such a small gauge machine that created the necessity to look to other arrangements in the first place.